Vehicle control device

Abstract

To perform brake switching control, while suppressing rattling shock in decelerating a vehicle in order to stop the vehicle.SOLUTION: During transition of brake switching control by which braking torque of a wheel is gradually increased while gradually decreasing regenerative braking torque and braking torque by the regenerative braking torque is switched to braking torque by the braking torque of the wheel in decelerating a vehicle in order to stop the vehicle, the gradual decrease of the regenerative braking torque is delayed for a predetermined period of time in a predetermined vicinity of zero just before the regenerative braking torque is set to zero, and the regenerative braking torque is gradually decreased toward zero after a predetermined time elapses, so that decrease of torque for play-filling caused by an electric motor is suppressed in the predetermined vicinity of zero during the brake switching control, which can set the regenerative braking torque to zero when the play-filling is performed sufficiently. This enables the brake switching control to be performed while suppressing the rattling shock in decelerating the vehicle in order to stop the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for a vehicle equipped with an electric motor that generates regenerative braking torque. [Background technology]

[0002] There is a well-known vehicle control device that includes an electric motor that generates a regenerative braking torque, which is a braking torque applied by regeneration, to a driving wheel, and a brake device that applies a wheel braking torque, which is a braking torque applied by a wheel brake, to the wheels including the driving wheel. For example, there is a vehicle braking control device described in Patent Document 1. Patent Document 1 discloses a method for suppressing a shock that occurs when switching between the regenerative braking torque and the wheel braking torque. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-56587 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when performing braking switching control in which the regenerative braking torque is gradually decreased while the wheel braking torque is gradually increased to switch the regenerative braking torque to the wheel braking torque, as the regenerative braking torque approaches zero [Nm], the clearance-reducing torque that presses one of the teeth faces against the other in the meshing portion that connects the electric motor and the rotating member to which the electric motor is connected decreases, and in addition, the torque that tries to rotate the electric motor from the driving wheel side, i.e., the driven torque, decreases due to the increase in the wheel braking torque, so that rattles are more likely to occur in the gaps in the meshing portions between the gears in the power transmission path between the electric motor and the driving wheels. The occurrence of rattles may lead to shocks associated with the clearance of the power transmission path being reduced, i.e., rattle shocks.

[0005] The present invention has been made against the background of the above circumstances, and its object is to provide a vehicle control device that can perform braking switching control while suppressing rattle shock when the vehicle decelerates toward a stop. [Means for solving the problem]

[0006] The gist of a first invention is a control device for a vehicle including: (a) an electric motor that generates a regenerative braking torque, which is a braking torque applied by regeneration, on drive wheels; and a brake device that applies a wheel braking torque, which is a braking torque applied by wheel brakes, to wheels including the drive wheels, (b) a braking control unit that performs braking switching control to switch the braking torque due to the regenerative braking torque to the braking torque due to the wheel braking torque by gradually increasing the wheel braking torque while gradually decreasing the regenerative braking torque, when the vehicle decelerates toward a stop; and (c) the braking control unit performs a braking switching control to stagnate the gradual decrease of the regenerative braking torque for a predetermined period of time near a predetermined zero before the regenerative braking torque is made zero, during a transition of the braking switching control, and gradually decrease the regenerative braking torque toward zero after the predetermined period has elapsed. (d) the braking control unit performs the braking switching control without stalling the gradual decrease of the regenerative braking torque when the braking torque is equal to or greater than a predetermined value, and performs the braking switching control to stall the gradual decrease of the regenerative braking torque for the predetermined time when the braking torque is less than the predetermined value. The point is... Effect of the Invention

[0007] According to the first aspect of the present invention, during a transition of braking switching control in which the regenerative braking torque is gradually decreased while the wheel braking torque is gradually increased to switch the braking torque due to the regenerative braking torque to the braking torque due to the wheel braking torque when the vehicle decelerates to stop, the gradual decrease of the regenerative braking torque is stalled for a predetermined time near a predetermined zero before the regenerative braking torque is made to be zero, and after the predetermined time has elapsed, the regenerative braking torque is gradually decreased toward zero, so that during the braking switching control, the decrease in the backlash eliminating torque by the electric motor is suppressed near the predetermined zero, and the regenerative braking torque is made to be zero when the backlash is sufficiently eliminated. Therefore, when the vehicle decelerates to stop, the braking switching control can be performed while suppressing rattle shock. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and a control system for various controls in the vehicle. [Diagram 2] 1 is a flowchart illustrating the main control operations of an electronic control device, and is a flowchart illustrating the control operations for performing brake switching control while suppressing rattle shock when the vehicle decelerates toward a stop. [Diagram 3] 3 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 2 is executed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0010] Fig. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining the main parts of the control functions and control system for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG that function as a power source SP. The vehicle 10 also has drive wheels 14 and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0011] The engine 12 is a known internal combustion engine such as a gasoline engine, a diesel engine, etc. An engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc., provided in the vehicle 10 is controlled by an electronic control device 90 described later, whereby an engine torque Te, which is an output torque of the engine 12, is controlled.

[0012] The electric motor MG is a rotating electric machine having a function as a motor that generates mechanical power from electric power and a function as a generator that generates electric power from mechanical power, and is a so-called motor generator. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The battery 54 is an electricity storage device that supplies and receives electric power to the electric motor MG. The electric motor MG controls the MG torque Tm, which is the output torque of the electric motor MG, by controlling the inverter 52 by an electronic control device 90 described later. For example, when the rotation direction of the electric motor MG is the same as the rotation direction when the engine 12 is in operation, the MG torque Tm is a powering torque Tmp for positive torque on the acceleration side, and a regenerative torque Tmr for negative torque on the deceleration side. Specifically, the electric motor MG generates power by electric power supplied from the battery 54. The electric motor MG generates electric power by the power of the engine 12 or the driven force input from the drive wheels 14 side. The battery 54 is charged with the electric power generated by the electric motor MG. The term "electric power" also means electric energy unless otherwise specified. The term "motive power" also means driving force, torque, and force unless otherwise specified.

[0013] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, in a case 18 that is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and the electric motor MG in a power transmission path between the engine 12 and the drive wheels 14. The torque converter 22 is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22 and is interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The torque converter 22 and the automatic transmission 24 each constitute a part of the power transmission path between the power source SP and the drive wheels 14. The power transmission device 16 also includes a propeller shaft 28 connected to a transmission output shaft 26 that is an output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, a pair of drive shafts 32 connected to the differential gear 30, and the like. The power transmission device 16 also includes an engine connecting shaft 34 that connects the engine 12 and the K0 clutch 20, an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22, and the like.

[0014] The electric motor MG is connected to the electric motor connecting shaft 36 in the case 18 so as to be capable of transmitting power. That is, the electric motor MG is connected to a power transmission path between the engine 12 and the drive wheels 14, in particular, to a power transmission path between the K0 clutch 20 and the torque converter 22. In other words, the electric motor MG is connected to the torque converter 22 and the automatic transmission 24 so as to be capable of transmitting power without passing through the K0 clutch 20.

[0015] The torque converter 22 includes a pump wheel 22a connected to the motor connecting shaft 36, and a turbine wheel 22b connected to a transmission input shaft 38 that is an input rotating member of the automatic transmission 24. The torque converter 22 is a fluid type power transmission device that transmits power from the power source SP from the motor connecting shaft 36 to the transmission input shaft 38 via fluid. The torque converter 22 includes an LU clutch 40 as a direct clutch that connects the pump wheel 22a and the turbine wheel 22b, that is, that connects the motor connecting shaft 36 and the transmission input shaft 38. The LU clutch 40 is a known lock-up clutch.

[0016] The automatic transmission 24 is a known planetary gear type automatic transmission that includes, for example, one or more planetary gear devices (not shown) and a plurality of engagement devices CB. The engagement devices CB are, for example, known hydraulic friction engagement devices. The engagement devices CB have their respective torque capacities, or CB torque Tcb, changed by the CB hydraulic pressure PRcb, which is a regulated hydraulic pressure supplied from a hydraulic control circuit 56 provided in the vehicle 10, thereby switching between operating states, i.e., control states, such as an engaged state, a slip state, a released state, and the like.

[0017] The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages (also called gear stages) with different speed ratios (also called gear ratios) γat (=AT input rotation speed Ni / AT output rotation speed No) is formed by engaging one of the engagement devices CB. The automatic transmission 24 switches between gear stages formed according to the accelerator operation of the driver (=operator) and the vehicle speed V by an electronic control device 90 described later. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38, and is the input rotation speed of the automatic transmission 24. The AT input rotation speed Ni is the same value as the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT input rotation speed Ni can be expressed by the turbine rotation speed Nt. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0018] The K0 clutch 20 is a hydraulic friction engagement device constituted by, for example, a multi-plate or single-plate clutch. The K0 clutch 20 switches between control states such as an engaged state, a slip state, and a released state by changing the torque capacity of the K0 clutch 20, which is a K0 torque Tk0, by the K0 hydraulic pressure PRk0, which is a regulated hydraulic pressure supplied from the hydraulic control circuit 56.

[0019] In the vehicle 10, when the K0 clutch 20 is in an engaged state, the engine 12 and the torque converter 22 are connected to each other so as to transmit power. On the other hand, when the K0 clutch 20 is in a disengaged state, power transmission between the engine 12 and the torque converter 22 is interrupted. Since the electric motor MG is connected to the torque converter 22, the K0 clutch 20 functions as a clutch that connects and disconnects the engine 12 from the electric motor MG.

[0020] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the driving wheels 14 via the K0 clutch 20, the electric motor connecting shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order. Moreover, the power output from the electric motor MG is transmitted from the electric motor connecting shaft 36 to the driving wheels 14 via the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order, regardless of the control state of the K0 clutch 20.

[0021] The vehicle 10 includes the MOP 58, which is a mechanical oil pump, the EOP 60, which is an electric oil pump, and a pump motor 62. The MOP 58 is connected to the pump impeller 22a, and is rotated by a power source SP to discharge hydraulic oil OIL used in the power transmission device 16. The pump motor 62 is a motor dedicated to the EOP 60 for rotating the EOP 60. The EOP 60 is rotated by the pump motor 62 to discharge hydraulic oil OIL. The hydraulic oil OIL discharged by the MOP 58 and the EOP 60 is supplied to a hydraulic control circuit 56. The hydraulic control circuit 56 supplies the CB hydraulic pressure PRcb, the K0 hydraulic pressure PRk0, and the like, which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60.

[0022] The vehicle 10 is equipped with a wheel brake device 64. The wheel brake device 64 includes a brake master cylinder and a cylinder actuator (not shown) that generate brake hydraulic pressure. The wheels WH, including the drive wheels 14 and the driven wheels (not shown), are each equipped with a wheel brake 66. If the vehicle 10 is an all-wheel drive vehicle, the driven wheels are the drive wheels. The wheel brake device 64 is a brake device that applies a wheel braking torque TBw, which is a braking torque TB by the wheel brake 66, to the wheel WH in accordance with a command from an electronic control device 90 (described later). The wheel brake device 64 supplies brake hydraulic pressure to wheel cylinders (not shown) provided in the wheel brakes 66 in response to, for example, the driver's depressing operation of the brake pedal. In the wheel brake device 64, under normal circumstances, a master cylinder hydraulic pressure corresponding to the brake operation amount Bra generated from the brake master cylinder is supplied to the wheel cylinder as brake hydraulic pressure. On the other hand, in the wheel brake device 64, for example, during ABS function operation, skid prevention control, vehicle speed control, automatic driving control, automatic brake function operation, regenerative control, etc., in order to generate wheel braking torque TBw, brake hydraulic pressure of a magnitude corresponding to the wheel braking torque TBw required for each control is supplied to the wheel cylinder. The brake operation amount Bra is a signal that corresponds to the brake pedal depression force and indicates the magnitude of the brake pedal depression operation by the driver, that is, the magnitude of the brake operation.

[0023] The vehicle 10 further includes an electronic control device 90 including a control device for the vehicle 10. The electronic control device 90 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, and the like, and the CPU executes various controls of the vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 90 includes computers for engine control, electric motor control, clutch control, and the like as necessary.

[0024] The electronic control device 90 receives various signals based on detection values ​​from various sensors provided in the vehicle 10 (for example, an engine rotation speed sensor 70, a turbine rotation speed sensor 72, an output rotation speed sensor 74, a MG rotation speed sensor 76, an accelerator opening sensor 78, a throttle valve opening sensor 80, a brake sensor 82, a battery sensor 84, an oil temperature sensor 86, etc.) (for example, an engine rotation speed Ne which is the rotation speed of the engine 12, a turbine rotation speed Nt which is the same value as the AT input rotation speed Ni, an AT output rotation speed No which corresponds to the vehicle speed V, a rotation speed of the electric motor MG which is the rotation speed of the electric motor MG, a vehicle speed V which corresponds to the vehicle speed V ... The following signals are respectively supplied: a certain MG rotation speed Nm, an accelerator opening θacc which is the amount of accelerator operation by the driver which indicates the magnitude of the driver's acceleration operation, a throttle valve opening θth which is the opening of the electronic throttle valve, a brake-on signal Bon which is a signal which indicates the state in which the brake pedal for operating the wheel brakes 66 is being operated by the driver, a brake operation amount Bra, a battery temperature THbat, a battery charge / discharge current Ibat and a battery voltage Vbat of the battery 54, and a hydraulic oil temperature THoil which is the temperature of the hydraulic oil OIL in the hydraulic control circuit 56.

[0025] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the electric motor MG, a CB hydraulic control command signal Sbc for controlling the engagement device CB, a K0 hydraulic control command signal Sk0 for controlling the K0 clutch 20, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, a brake control command signal Sbra for controlling the wheel braking torque TBw, etc.) to each device provided in the vehicle 10 (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, the wheel brake device 64, etc.).

[0026] In order to realize various controls in the vehicle 10, the electronic control unit 90 includes a power source control means, i.e., a power source control section 92, a clutch control means, i.e., a clutch control section 94, and a braking control means, i.e., a braking control section 96.

[0027] The power source control unit 92 includes a function as engine control means, i.e., engine control unit 92a, that controls the operation of the engine 12, and a function as electric motor control means, i.e., electric motor control unit 92b, that controls the operation of the electric motor MG via the inverter 52, and is a hybrid control means, i.e., a hybrid control unit, that performs hybrid drive control by the engine 12 and the electric motor MG using these control functions.

[0028] The power source control unit 92 calculates the driving demand amount of the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand amount map. The driving demand amount map is a relationship that is experimentally or design-wise obtained and stored in advance, that is, a predetermined relationship. The driving demand amount is, for example, a required driving torque Trdem at the driving wheels 14. In other words, the required driving torque Trdem [Nm] is a required driving power Prdem [W] at the vehicle speed V at that time. As the driving demand amount, a required driving force Frdem [N] at the driving wheels 14, a required AT output torque at the transmission output shaft 26, etc. can also be used. In calculating the driving demand amount, an AT output rotation speed No, etc. may be used instead of the vehicle speed V. The power source control unit 92 outputs an engine control command signal Se for controlling the engine 12 and an MG control command signal Sm for controlling the electric motor MG so as to realize the required driving power Prdem, taking into account a transmission loss, an auxiliary load, a gear ratio γat of the automatic transmission 24, etc.

[0029] When the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the power source control unit 92 sets the drive mode for driving the vehicle 10 to the BEV drive mode. The BEV drive mode is a motor drive mode that allows motor driving (=BEV driving) in which the vehicle runs using only the electric motor MG as the power source SP when the K0 clutch 20 is in the released state. On the other hand, when the required drive torque Trdem cannot be satisfied without using at least the output of the engine 12, the power source control unit 92 sets the drive mode to the engine drive mode, i.e., the HEV drive mode. The HEV drive mode is a hybrid drive mode that allows engine driving (=HEV driving) in which the vehicle runs using at least the engine 12 as the power source SP when the K0 clutch 20 is in the engaged state. On the other hand, even when the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the power source control unit 92 establishes the HEV drive mode when the battery 54 needs to be charged or when the engine 12 or the like needs to be warmed up.

[0030] The power source control unit 92, particularly the engine control unit 92a, determines whether or not there is an engine start request to switch the control state of the engine 12 from a stopped state to an operating state. For example, in the BEV drive mode, the engine control unit 92a determines whether or not there is an engine start request based on whether or not the required drive torque Trdem has increased beyond a range that can be covered only by the output of the electric motor MG, whether or not there is a need to warm up the engine 12, or whether or not there is a need to charge the battery 54.

[0031] When the power source control unit 92 determines that there is an engine start request, the clutch control unit 94 controls the K0 clutch 20 to execute start control of the engine 12. For example, the clutch control unit 94 outputs a K0 hydraulic pressure command value Spk0 for controlling the K0 clutch 20 from a released state toward an engaged state so as to obtain a K0 torque Tk0 for transmitting the cranking torque Tcr to the engine 12. The cranking torque Tcr is a torque required for cranking the engine 12 to increase the engine rotation speed Ne.

[0032] When it is determined that there is an engine start request, the power source control unit 92 controls the engine 12 and the electric motor MG to execute start control of the engine 12. For example, the electric motor control unit 92b outputs an MG control command signal Sm to the inverter 52 in response to switching of the K0 clutch 20 to the engaged state, so that the electric motor MG outputs a cranking torque Tcr. Furthermore, the engine control unit 92a outputs an engine control command signal Se to the engine control device 50 in response to the cranking of the engine 12, so as to start fuel supply, engine ignition, and the like.

[0033] The clutch control unit 94 judges whether or not the automatic transmission 24 should be shifted by using, for example, a shift map which is a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 to execute shift control of the automatic transmission 24 as necessary. The shift map is a predetermined relationship having a shift line for judging whether or not the automatic transmission 24 should be shifted on a two-dimensional coordinate system having, for example, vehicle speed V and required driving torque Trdem as variables. In the shift map, the AT output rotation speed No may be used instead of the vehicle speed V, and the required driving force Frdem, accelerator opening θacc, throttle valve opening θth, etc. may be used instead of the required driving torque Trdem.

[0034] The braking control unit 96 sets the required braking torque TBdem based on, for example, the accelerator operation by the driver (e.g., accelerator opening θacc, the rate of decrease in accelerator opening θacc), the vehicle speed V, the gradient of a downhill road, the braking operation by the driver to activate the wheel brakes 66 (e.g., the brake operation amount Bra, the rate of increase in the brake operation amount Bra), etc. The braking control unit 96 generates the braking torque TB of the vehicle 10 so as to obtain the required braking torque TBdem while the vehicle 10 is decelerating. The side where the braking torque TB (<0) is small is the side where the absolute value of the braking torque TB is large, but for convenience, for example, increasing the absolute value of the braking torque TB will be expressed simply as increasing the braking torque TB, i.e., increasing the braking torque TB, and decreasing the absolute value of the braking torque TB will be expressed simply as decreasing the braking torque TB, i.e., decreasing the braking torque TB.

[0035] The required braking torque TBdem is basically a required braking torque for the wheel braking torque TBw by the wheel brake device 64, and is realized by the wheel braking torque TBw, but is realized preferentially by the regenerative braking torque TBr from the viewpoint of improving energy efficiency, for example. The braking torque TB that realizes the required braking torque TBdem is generated by, for example, the regenerative braking torque TBr and the wheel braking torque TBw. The regenerative braking torque TBr is a braking torque TB obtained by braking due to regeneration of the electric motor MG. In other words, the electric motor MG generates a regenerative braking torque TBr, which is a braking torque TB due to regeneration, on the driving wheels 14. The regenerative torque Tmr of the electric motor MG is the MG torque Tm during regeneration of the electric motor MG, which is obtained by converting the regenerative braking torque TBr at the driving wheels 14 onto the electric motor connecting shaft 36 based on the speed ratio γat of the automatic transmission 24 and the reduction ratio of the differential gear 30, etc. The regeneration of the electric motor MG is a control in which the electric motor MG is rotationally driven by the driven torque input from the drive wheels 14 to operate as a generator, and the generated electric power of the electric motor MG is charged into the battery 54.

[0036] When the required braking torque TBdem can be entirely covered by the regenerative braking torque TBr, the braking control unit 96 sets the required regenerative braking torque TBr as the required braking torque TBdem. When the absolute value of the required braking torque TBdem is greater than the absolute value of the upper limit of the regenerative braking torque TBr and therefore only a portion of the required braking torque TBdem can be covered by the regenerative braking torque TBr, the braking control unit 96 sets the required regenerative braking torque TBr as the upper limit of the regenerative braking torque TBr and sets the required wheel braking torque TBw as the other portion of the required braking torque TBdem that cannot be covered by the regenerative braking torque TBr.

[0037] The braking control unit 96 outputs a command to the motor control unit 92b to execute regenerative control by the motor MG so as to obtain a regenerative torque Tmr for realizing the required regenerative braking torque TBr. The motor control unit 92b outputs an MG control command signal Sm to perform regenerative control of the motor MG so as to obtain the regenerative torque Tmr for realizing the required regenerative braking torque TBr. The braking control unit 96 outputs a brake control command signal Sbra to the wheel brake device 64 to operate the wheel brake 66 so as to obtain the required wheel braking torque TBw.

[0038] When the vehicle 10 is approaching a stop and regenerative control of the electric motor MG is being performed, the braking control unit 96 gradually switches the braking torque TB due to the regenerative braking torque TBr to the braking torque TB due to the wheel braking torque TBw while realizing the required braking torque TBdem. In other words, before the vehicle 10 stops, the braking control unit 96 gradually replaces the regenerative braking torque TBr with the wheel braking torque TBw to realize the required braking torque TBdem. In this way, when the vehicle 10 decelerates toward a stop, the braking control unit 96 performs braking switching control CTtbch that gradually reduces the regenerative braking torque TBr while gradually increasing the wheel braking torque TBw, thereby switching the braking torque TB due to the regenerative braking torque TBr to the braking torque TB due to the wheel braking torque TBw.

[0039] Incidentally, when the brake switching control CTtbch is performed, as the regenerative braking torque TBr approaches zero [Nm], the backlash-removing torque that removes backlash in the meshing portion connecting the electric motor MG and the electric motor connecting shaft 36 decreases. In addition, the driven torque decreases due to an increase in the wheel braking torque TBw accompanying the brake switching control CTtbch. Therefore, rattles are likely to occur in the gaps in the meshing portions between the gears in the power transmission path between the electric motor MG and the drive wheels 14, which may cause rattle shocks.

[0040] Therefore, when performing the braking switching control CTtbch, the braking control unit 96 does not reduce the regenerative torque Tmr at a constant gradient to zero [Nm], but rather provides a time for slowly eliminating the backlash while leaving a small amount of backlash elimination torque due to the regenerative torque Tmr, and makes the regenerative torque Tmr zero when the backlash elimination is sufficiently completed. For example, when performing the braking switching control CTtbch, the braking control unit 96 provides a temporary shelf in the change state of the regenerative torque Tmr when the gradually decreasing regenerative torque Tmr approaches zero. In other words, during the transition of the braking switching control CTtbch, the braking control unit 96 stalls the gradual decrease of the regenerative braking torque TBr at a predetermined near-zero TBrf for a predetermined time TMf before making the regenerative braking torque TBr zero, and gradually decreases the regenerative braking torque TBr toward zero after the predetermined time TMf has elapsed. The predetermined near-zero TBrf is, for example, a value of the regenerative braking torque TBr at which a small amount of backlash-reducing torque remains due to the regenerative torque Tmr, and is a value just before the predetermined regenerative braking torque TBr at which backlash can be sufficiently eliminated when the driven torque is reduced becomes zero. The predetermined time TMf is, for example, a predetermined period at which backlash can be sufficiently eliminated by the regenerative braking torque TBr of the predetermined near-zero TBrf.

[0041] When the gradual decrease of the regenerative braking torque TBr is stalled for a predetermined time TMf at a predetermined zero vicinity TBrf, that is, when a shelf is provided in the regenerative torque Tmr, the timing at which the brake switching control CTtbch is completed, that is, the timing at which the regenerative braking torque TBr becomes zero [Nm], is delayed by the predetermined time TMf. Therefore, when a shelf is provided in the regenerative torque Tmr, the brake control unit 96 advances the timing of the execution of the brake switching control CTtbch by the predetermined time TMf compared to when a shelf is not provided in the regenerative torque Tmr. Advancing the timing of the execution of the brake switching control CTtbch by the predetermined time TMf means that the brake switching control CTtbch is started earlier with respect to the decrease in the vehicle speed V during deceleration, that is, at a higher vehicle speed, compared to when the shelf is not advanced by the predetermined time TMf.

[0042] If the start timing of the brake switching control CTtbch is advanced, the regenerative braking torque TBr will decrease earlier, which is disadvantageous in terms of improving energy efficiency. On the other hand, when the required braking torque TBdem is large, the regenerative braking torque TBr will be increased, making it easier to improve energy efficiency, and the deceleration of the vehicle 10 will be increased, which may make the rattle shock less noticeable. On the other hand, when the required braking torque TBdem is small, the regenerative braking torque TBr will be reduced, making it harder to improve energy efficiency, and the deceleration of the vehicle 10 will be reduced, which may make the rattle shock more noticeable.

[0043] From the above viewpoint, when the required braking torque TBdem is equal to or greater than the predetermined value TBf, the braking control unit 96 executes normal braking switching control CTtbch in which a shelf is not provided in the regenerative torque Tmr, and prioritizes improving energy efficiency. On the other hand, when the required braking torque TBdem is less than the predetermined value TBf, the braking control unit 96 executes forward braking switching control CTtbch in which a shelf is provided in the regenerative torque Tmr, and prioritizes suppressing the rattle shock. The predetermined value TBf is, for example, a value whose absolute value is smaller than the upper limit value of the regenerative braking torque TBr, and is a predetermined threshold value for determining that the required braking torque TBdem is one for which suppressing the rattle shock should be prioritized over improving energy efficiency. In other words, when performing the braking switching control CTtbch, whether or not a shelf is provided in the regenerative torque Tmr is variable depending on the deceleration, so that both suppressing the rattle shock and improving energy efficiency can be achieved.

[0044] Considering the case where the normal braking switching control CTtbch is started while the regenerative control by the electric motor MG is being executed, when the vehicle speed V is equal to or lower than the vehicle speed V at which the normal braking switching control CTtbch is started, it is necessary to determine whether the required braking torque TBdem is equal to or higher than a predetermined value TBf or lower than the predetermined value TBf. When the braking control unit 96 determines that the vehicle speed V is equal to or lower than the vehicle speed V at which the normal braking switching control CTtbch is started, the braking control unit 96 determines whether the required braking torque TBdem is lower than the predetermined value TBf. In this embodiment, the vehicle speed V at which the normal braking switching control CTtbch is started is referred to as the regenerative switching gradient determination vehicle speed Vr.

[0045] Fig. 2 is a flowchart for explaining the main part of the control operation of the electronic control device 90, and is a flowchart for explaining the control operation for performing the brake switching control CTtbch while suppressing the rattle shock when the vehicle 10 decelerates toward a stop, and is executed, for example, repeatedly. Fig. 3 is a diagram showing an example of a time chart when the control operation shown in the flowchart of Fig. 2 is executed.

[0046] In FIG. 2, each step of the flowchart corresponds to a function of the braking control unit 96. In step (hereinafter, step will be omitted) S10, it is determined whether the vehicle speed V is equal to or lower than the regenerative switching gradient determination vehicle speed Vr. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, it is determined in S20 whether the required braking torque TBdem is less than a predetermined value TBf. If the determination in S20 is positive, in S30, a forward braking switching control CTtbch is executed, which provides a shelf in the regenerative torque Tmr, and suppression of rattle shock is prioritized. If the determination in S20 is negative, in S40, a normal braking switching control CTtbch is executed, which does not provide a shelf in the regenerative torque Tmr, and improvement of energy efficiency is prioritized.

[0047] FIG. 3 is a diagram showing an example of a case where normal braking switching control CTtbch is executed and a case where front-pushing braking switching control CTtbch is executed. In FIG. 3, vehicle speed V1 is vehicle speed V corresponding to regenerative switching gradient determination vehicle speed Vr. It is determined whether the required braking torque TBdem is equal to or greater than a predetermined value TBf or less than the predetermined value TBf at the vehicle speed V1. The "regenerative front-pushing lower limit torque" in the figure is the value Tmrlim of the regenerative torque Tmr obtained by converting the predetermined value TBf onto the motor connecting shaft 36. When the vehicle speed is equal to or less than V1, once it is determined whether the required braking torque TBdem is equal to or greater than the predetermined value TBf or less than the predetermined value TBf, it is desirable not to change the determination until the regenerative control by the electric motor MG ends. In other words, once S20 in FIG. 2 described above is executed, the determination of S20 is maintained until the regenerative control by the electric motor MG ends. Therefore, once the vehicle speed falls below the regenerative switching gradient determination vehicle speed Vr, the regenerative torque Tmr cannot be increased even if the brake pedal is depressed further. The thin solid line A shows the change state of the normal regenerative torque Tmr when the normal braking switching control CTtbch is executed, which is executed when the required braking torque TBdem is equal to or greater than the predetermined value TBf, that is, when the regenerative torque Tmr is equal to or greater than the regenerative front-out lower limit torque Tmrlim. The thick solid line B shows the change state of the front-out regenerative torque Tmr when the front-out braking switching control CTtbch is executed, which is executed when the required braking torque TBdem is less than the predetermined value TBf, that is, when the regenerative torque Tmr is less than the regenerative front-out lower limit torque Tmrlim. The normal regenerative torque Tmr shown in the thin solid line A is gradually decreased from the upper limit value toward zero at a constant change gradient by starting the normal braking switching control CTtbch from the vehicle speed V1, and is set to zero at the vehicle speed V4 without providing a shelf. This gives priority to improving energy efficiency. The front-output regenerative torque Tmr shown by the thick solid line B is gradually reduced at a constant change gradient from the regenerative front-output lower limit torque Tmrlim by starting the front-output braking switching control CTtbch from the vehicle speed V2 where the braking torque TB is less than a predetermined value TBf, that is, where the regenerative torque Tmr is less than the regenerative front-output lower limit torque Tmrlim.The front-pushing regenerative torque Tmr has a shelf near the vehicle speed V3 where the regenerative braking torque TBr becomes a predetermined zero vicinity TBrf during the gradual decrease transition, and the gradual decrease is stalled for a predetermined time TMf to eliminate backlash, and then the torque is gradually decreased toward zero and becomes zero at the vehicle speed V4. This prioritizes suppression of rattle shock. Also, the front-pushing brake switching control CTtbch is completed at a vehicle speed V equivalent to that of the normal brake switching control CTtbch. The front-pushing regenerative torque Tmr shown by the thick solid line B is changed in an area below the regenerative front-pushing lower limit torque Tmrlim, but if it were to be gradually decreased from the upper limit value, the front-pushing brake switching control CTtbch would be started at a vehicle speed V0, which is higher than the vehicle speed V1, and the change state shown by the dashed line C would be obtained.

[0048] As described above, according to this embodiment, during the transition of the brake switching control CTtbch, when the vehicle 10 decelerates toward a stop, the gradual decrease of the regenerative braking torque TBr is stalled for a predetermined time TMf at a predetermined near-zero TBrf before the regenerative braking torque TBr is set to zero, and after the predetermined time TMf has elapsed, the regenerative braking torque TBr is gradually decreased toward zero, so that during the brake switching control CTtbch, the decrease in the backlash eliminating torque by the electric motor MG is suppressed at the predetermined near-zero TBrf, and the regenerative braking torque TBr is set to zero when backlash is sufficiently eliminated. Therefore, when the vehicle 10 decelerates toward a stop, the brake switching control CTtbch can be performed while suppressing rattle shock.

[0049] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention can be applied to other embodiments.

[0050] For example, in the above embodiment, the required braking torque TBdem is set based on the brake operation by the driver, but this is not limited to the above. For example, the required braking torque TBdem may be set based on a brake request in a known automatic driving control, or a brake request in a known automobile speed control.

[0051] In the above embodiment, it is determined whether the required braking torque TBdem is equal to or greater than the predetermined value TBf or less than the predetermined value TBf, but the present invention is not limited to this. For example, the actual braking torque TB (actual regenerative braking torque TBr+actual wheel braking torque TBw) may be used instead of the required braking torque TBdem. The actual regenerative braking torque TBr and the wheel braking torque TBw are calculated based on, for example, the respective command signals.

[0052] In the above embodiment, whether or not to provide a shelf in the regenerative torque Tmr is switched based on whether or not the required braking torque TBdem is less than the predetermined value TBf, but this is not the only possible embodiment. For example, when performing the braking switching control CTtbch, a shelf may be provided in the regenerative torque Tmr at all times, regardless of whether the required braking torque TBdem is less than the predetermined value TBf.

[0053] In the above embodiment, the vehicle 10 including the engine 12, the electric motor MG, and the automatic transmission 24 is exemplified as a vehicle to which the present invention is applied, but the present invention is not limited to this embodiment. For example, the present invention can be applied to an electric vehicle that does not include an engine and uses only an electric motor as a power source SP, a hybrid vehicle that includes a known electric continuously variable transmission, etc. In addition, the automatic transmission 24 may be a synchronous mesh type parallel two-shaft automatic transmission including a known DCT (Dual Clutch Transmission), a known belt type continuously variable transmission, etc. In short, the present invention can be applied to any vehicle that includes an electric motor that generates regenerative braking torque and a brake device that applies wheel braking torque.

[0054] In the above embodiment, the torque converter 22 is used as the fluid transmission device, but the present invention is not limited to this. For example, instead of the torque converter 22, another fluid transmission device that does not amplify torque, such as a fluid coupling, may be used as the fluid transmission device. Alternatively, the fluid transmission device does not necessarily have to be provided, and may be replaced with, for example, a starting clutch.

[0055] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0056] 10: Vehicle 14: Drive wheel 64: Wheel brake device (brake device) 66: Wheel brake 90: Electronic control device (control device) 96: Braking control unit MG: Electric motor WH: Wheel

Claims

[Claim 1] A control device for a vehicle including an electric motor that generates a regenerative braking torque, which is a braking torque by regeneration, on a driving wheel, and a brake device that applies a wheel braking torque, which is a braking torque by a wheel brake, to a wheel including the driving wheel, comprising: a braking control unit that performs braking switching control to switch the braking torque due to the regenerative braking torque to the braking torque due to the wheel braking torque by gradually increasing the wheel braking torque while gradually decreasing the regenerative braking torque when the vehicle is decelerating toward a stop, the braking control unit, during a transition of the braking switching control, halts the gradual decrease of the regenerative braking torque for a predetermined time at a predetermined vicinity of zero before the regenerative braking torque is made zero, and gradually decreases the regenerative braking torque toward zero after the predetermined time has elapsed; A vehicle control device characterized in that the braking control unit performs the braking switching control without stalling the gradual decrease of the regenerative braking torque when the braking torque is equal to or greater than a predetermined value, and performs the braking switching control by stalling the gradual decrease of the regenerative braking torque for the predetermined time when the braking torque is less than the predetermined value.

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